Originally Posted by
TerryK
Yes, this is normal if you want to change your outbound leg. Once you have flown at least one segment, no refare is required to change.
IIRC there can be exceptions when red eyes are involved.
Another exception would be if the trip had been ticketed as two or more one ways rather than a RT or a single multicity ticket/itinerary. This illustrates some of the advantages and disadvantages of having a single ticket/PNR when the fares used price on a one way basis.
Doing a SDC wouldn't help the OP to save money; there aren't refunds when you SDC to cheaper flights. I'm not sure whether the OP was trying to save money or simply wants to make the change, but I suspect the latter is the motivation here.